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Spatial and temporal temperature variations in bridge structures due to changes in the surrounding climate cause bridge expansion which, if restrained, may induce secondary stresses in structures. Temperature effects have always been considered to be one of the most critical issues in the performance of traditional Prestressed Concrete (PC) bridges. In order to (1) develop an efficient temperature loading model for predicting bridge temperature-induced response; and (2) develop guidelines addressing the effects of temperature loading in reliability-based condition evaluation, numerical and analytical studies were conducted on a PC girder bridge in Oklahoma, USA. This paper focuses on the probabilistic modelling of temperature loading. Firstly, a heat transfer model was established using hourly input climate data to estimate the temperature distribution, and compared with monitoring counterparts for calibration. Secondly, the validated analytical model was employed to investigate the effects of thermal properties of concrete by a parametric analysis; Based on extreme environmental conditions from the 20-year climatic data and analytical results, probabilistic models of uniformly distributed temperature fields and temperature gradients were proposed, and the temperature loading value with a 75-year return period was determined and compared with recommended value in the AASHTO LRFD. The proposed temperature loading model can aid engineers in predicting the thermal behavior of PC bridges in Oklahoma, USA.

Spatial and temporal temperature variations in bridge structures due to changes in the surrounding climate produce movements which, if restrained, may induce stresses in the structure. Temperature effects have always been considered to be one of the critical issues that affect the performance of prestressed concrete (PC) bridges. In order to (1) develop an efficient temperature loading model for predicting bridge temperature-induced response; and (2) develop guidelines to incorporate the effects of temperature actions in reliability-based condition evaluation, numerical and analytical studies were conducted on a PC girder bridge in Oklahoma, USA. This paper focuses on the structural reliability analysis on the temperature loading action in accordance with AASHTO LRFD specification. A three-dimensional (3D) finite element method (FEM) model was established to estimate the movement and stress under temperature loading, and compared with monitoring counterparts. Then, the validated model was utilized for probabilistic analyses to assess the temperature load effects. Based on the probabilistic temperature loading model proposed in the first paper, loads and resistances statistics from published literature, reliability analyses of AASHTO LRFD limit states were performed by Monte Carlo simulation (MCS) and Rackwitz-Fiessler procedure to determine the safety level in terms of reliability index.

Although several old riveted bridges served more than 100–150 years in the world, some of them are still in the application, generally limited by the economic budget or cultural relic protection reason. Hence, the status of those bridges needed to be evaluated to support the bridge management and rehabilitation, especially with the increasing traffic flow along with their service life. Nowadays, fatigue detail class 71 in the EN 1993-1-9 is generally recommended to evaluate the fatigue behaviour of the riveted joints. But the predicted fatigue behaviour of riveted connection using the recommended S-N curves is excessive conservative because the differences of connection geometries and materials are not fully considered using the global nominal stress methods. Therefore, in this paper, a two-phase fatigue performance approach based on local strain and Paris law, respectively, fatigue crack initiation and propagation phases, combined with numerical simulation, is an effective surrogate method to predict the fatigue performance of riveted connections, considering the material and geometry effects. A good agreement is observed when compared to numerical simulation with experimental observations.

Offshore structures have a long service life and involve high cost. However, the working environment of offshore structures is harsh. When an accident occurs, it causes an adverse social impact and economic loss. Therefore, in the design process of offshore structures, in order to enhance their safety, this is an important problem that needs attention. Reliability-based design and optimisation (RBDO) using saddlepoint approximation (SA) is a powerful method to enhance the reliability of offshore structures. The SA utilises a cumulant generating function and saddlepoint to approximately express the probability density function and cumulative distribution function of a limit-state function. To further improve the accuracy of reliability evaluation in RBDO with SA, in this study, a mean-value second-order SA (MVSOSA) is introduced. A RBDO with MVSOSA strategy is proposed for the design problem of a wellhead platform. An engineering case study illustrates the application of the proposed method.

Multiaxial fatigue is frequently present on engineering structures and is the cause of many mechanical failures. However, multiaxial fatigue analysis is full of questions and different points of view. Thus, throughout this study, Susmel’s criterion, a recent multiaxial fatigue damage model also known as the Modified Wohler Curve Method, is presented, explained and assessed. Experimental data of axial, torsional and proportional (axial+torsional) fatigue tests conducted on S355 structural steel and under different stress ratios were analysed and evaluated according to this model. Mean fatigue design curves for each loading condition were obtained and plotted in the high cycle fatigue region. Finally, the ability of Susmel’s criterion to assess the multiaxial fatigue behaviour of S355 steel in the high cycle region was evaluated by determining the error index between the theoretically estimated and the experimental fatigue damage. Susmel’s model was found to be adequate to describe the fatigue behaviour of the steel under study in high cycle region.

Together with the development of numerical tools for stress-strain analysis, approaches to deal with fracture mechanics problems have been the object of continuous improvement. For linear-elastic fracture mechanics problems, the determination of Stress Intensity Factors (SIF) is available as a post-processing possibility in most commercial finite element software packages such as Ansys and Abaqus, allowing the users to perform straightforward assessments of cracked mechanical parts or structures. However, available techniques for SIF determination in post-processing of these commercial solutions are almost limited to the so-called displacement extrapolation and J-integral techniques. In the present work, the implementation of the J-integral technique is revised considering a new finite element software, labeled as Omicron. Furthermore, a more recent technique, the modified Virtual Crack Closure Technique (mVCCT) is also implemented and evaluated. For results assessment, finite element models were built in Omicron and SIFs were determined considering the J-integral and mVCCT approaches. From this study, it is concluded that the mVCCT implementation is simpler than the J-integral and it allows to determine accurately SIFs. Nevertheless, this technique is not straightly available in the current versions of the commercial packages for finite element modeling, which require separate post-processing for SIF determination.

In large companies, warehouse logistics usually include shuttle pallet carriers that are responsible for the transportation of various goods and products. These shuttles run along steel rails, which are usually produced from thin metal sheets that are cold roll-formed into the desired section. These shuttles also work 24 hours a day, 7 days a week, so the rails are very sensitive to fatigue phenomena, caused by the cyclic loading of the moving shuttles, moreover, cracks due to material fatigue have already been observed in these types of rails. In addition, the competitiveness of the European industrial sector is pushing the design of these profiles to lower thickness requirements, which further increases concerns about their fatigue performance. Within this background, the FASTCOLD European project has been carried out, whose research plan consists in developing fatigue design rules for the mentioned applications, which are not covered by existing Eurocode 3 rules, which only addresses thick hot-rolled sections. Experimental fatigue testing has been carried out backed by numerical simulations of these tests. A new fatigue setup has been developed to generate representative fatigue cracking to the shuttle cyclic loads. Numerical simulations of the cold roll-forming fabrication process are also being carried out to determine the importance of the residual stresses in the fatigue life of the rail. With the experimental data obtained from fatigue testing backed by numerical simulations, important contributions are made to the design codes (e.g. Eurocode 3) in dealing with the fatigue design of such critical details.

PurposeEngineered stone is a material which can be described as an artificial stone. The exemplary application area is sink production. There are very few research projects about this type of material. In fact, most of them are research conducted by the manufacturing company, which are limited to the basic properties of the material. However, knowledge about fracture mechanic of this material may be crucial in terms of usage. The paper aims to discuss this issue.Design/methodology/approachAnalysis of the inside structure was made using an optical microscope as well as SEM. In the paper, methods which can be used to obtain data about fracture behaviour of material are presented. Using eXtended Finite Element Method and experimental data from three-point bending of notched specimens stress intensity factors (SIFs) for I and II load modes were obtained. Finally, a comparison between the fracture initiation angle in the function of the ration of SIFs for I/II load modes and maximum tangential stress hypothesis prediction was presented.FindingsAnalysis of the inside structure proves that this type of material has an uneven distribution of particle size. This can follow to void and micronotches formation and, later, to the failure of the material. A method of obtaining stress intensity factors for the discussed type of material and specimens can be successfully applied to other similar material, as proposed in this work. Standard crack angle propagation criteria are not sufficient for this type of material.Originality/valueThere are very few research papers about this type of material. The subject of fracture mechanic is not properly discovered, despite the fact that IT is important in terms of the application area of these materials.

Modeling of the notch and size effects on fatigue behavior of materials is vital for ensuring structural integrity and reliability of engineering components. This study presents a methodology considering both effects of notch and size to analyze the fatigue life distribution of specimens with different geometries using the highly stressed volume approach. Specifically, a dynamic model coefficient considering the influence of different maximum local stresses is developed by modeling the size effect of highly stressed volumes with Weibull distribution. Experimental data of three aluminum and titanium alloys are utilized for model validation and comparison. Fatigue lives of three materials with different geometries are evaluated respectively, and predicted P-S-N curves indicate that proposed model predictions agree well with the probabilistic scatter band of experimental results.

Purpose The purpose of this paper is to evaluate the fatigue process through the dynamic analysis of the global structural model and local static sub-modelling in a critical detail using the hot-spot stress approach. The detail was studied in three different positions at the “Alcácer do Sal” access viaduct, and the methodologies from the IIW and Eurocode EN 1993-1-9 were compared. Design/methodology/approach In this study, the fatigue life process based on the hot-spot stress approach was evaluated using a global dynamic analysis and a local sub-modelling based on a static analysis of welded connections in the “Alcácer do Sal” railway structure, Portugal, taking into consideration the recommendations from IIW and Eurocode EN 1993-1-9. The hot-spot stresses were calculated through the static analysis of the sub-model of the welded connection for each vibration mode with the aim to obtain the temporal stresses using the modal coordinates and modal stresses of the extrapolation points. The Ansys® and Matlab® softwares were used for the numerical analysis and the hot-spot stress calculations, respectively. Findings The proposed methodology/approach to obtain fatigue assessment is based on the modal analysis of the global structural model and local static sub-modelling. The modal analysis was used to extract the boundary conditions to be used in the local model to determine the temporal stresses of the extrapolation points. Based on the modal superposition method, the stresses as function of time were obtained for fatigue life evaluation of a critical detail by the hot-spot stress approach. The detail was studied in three different positions. Originality/value In the present study, a global-local fatigue methodology based on dynamic analysis of the global structural model and local static sub-modelling of the critical detail using the hot-spot stress approach is proposed. Herein, the modal analysis of the global structural model supported by the modal superposition method was used to obtain the matrix of modal coordinates. The static analysis of the local sub-model for each mode from the modal analysis of global structural model was done to estimate the hot-spot stresses. The fatigue damage calculation was based on S-N curve of the critical detail and rainflow method. The IIW recommendation proved to be more conservative compared to the proposed rules in the Eurocode EN 1993-1-9. The global-local modelling based on dynamic analysis is an important and effective tool for fatigue evaluation in welded joints.

The reliable performance of composite tubes conveying nanofluid is an essential issue for robust design under dynamic loads. Further, the frequency failure mode of these structures is a considerable performance function to provide a balance between mass and stiffness of the structure. The ability of the first-order reliability method (FORM)-based finite-step adaptive length (FAL) is discussed for reliability analysis of composite tubes under frequency failure mode. The performances for efficiency and robustness to evaluate the failure probability FORM formulas are discussed. Therefore, the capability of FAL using the steepest descent sensitivity vector is compared with three FORM formulations that are extended by the steepest descent search direction for nanocomposite tubes conveying nanofluid. In this current work, the Navier scheme is employed for calculating the frequency failure mode. Furthermore, the robustness and efficiency related to the steepest descent FORM formulas of HL-RF, directional stability transformation method (DSTM), and finite-step length (FSL) are compared with FAL. Based on this discussion, FAL contains efficient formula in comparison with other FORM formulas. Moreover, it is found that FSL formulas as well as FAL formulas are more robust than HL-RF and DSTM. This structure's failure probability rises as the fluid velocity and pipe diameter increase.

PurposeIn the last decades, the demand and use of renewable energies have been increasing. The increase in renewable energies, particularly wind energy, leads to the development and innovation of powerful wind energy converters as well as increased production requirements. Hence, a higher supporting structure is required to achieve higher wind speed with less turbulence. To date, the onshore wind towers with tubular connections are the most used. The maximum diameter of this type of tower is limited by transportation logistics. The purpose of this paper is to propose an alternative wind turbine lattice structure based on half-pipe steel connections.Design/methodology/approachIn this study, a new concept of steel hybrid tower has been proposed. The focus of this work is the development of a lattice structure. Therefore, the geometry of the lattice part of the tower is assessed to decrease the number of joints and bolts. The sections used in the lattice structure are constructed in a polygonal shape. The elements are obtained by cold forming and bolted along the length. The members are connected by gusset plates and preloaded bolts. A numerical investigation of joints is carried out using the finite element (FE) software ABAQUS.FindingsBased on the proposed study, the six “legs” solution with K braces under 45° angle and height/spread ratio of 4/1 and 5/1 provides the most suitable balance between the weight of the supporting structure, number of bolts in joints and reaction forces in the foundations, when compared with four “legs” solution.Originality/valueIn this investigation, the failure modes of elements and joints of an alternative wind turbine lattice structures, as well as the rotation stiffness of the joints, are determined. The FE results show good agreement with the analytical calculation proposed by EC3-1-8 standard.

Fatigue failures are a concern for old riveted steel bridges since most of them were not originally designed taking into account fatigue. The usual fatigue assessment approach for riveted joints consists of using the fatigue class 71 S-N curve proposed in Eurocode 3, part 1–9. However, this approach may lead to excessive conservative predictions since it is applied indistinctly for different riveted connection geometries and materials. Riveted joints fatigue classification according to the proposal of Taras and Greiner produce more consistent description of the experimental data rather than the Class 71 S-N curve as proposed in the EC3. Local approaches are an alternative methodology to perform fatigue characterization of any type of joints, made of any material, providing that material fatigue properties are available as well as accurate numerical models of the joints. This paper presents an experimental campaign and a numerical analysis concerning down-scale riveted specimens. The fatigue behaviour of these riveted joints was also modelled using standard and extended finite element methods. The different models produced diverse predictions, depending on the failure modes considered.

Engineering components made of ductile cast irons and aluminum alloys, show fatigue lives which are normally dominated by crack initiation from defects raised by manufacturing processes. This study presents a probabilistic model to account for the influence of manufacturing defects on fatigue life, based on size and position of those defects. Specifically, a correction factor considering the influence of defect surface position is developed by modeling the damage mechanism of surface initial cracks with Weibull distribution. Experimental data of three cast irons and aluminum alloys are used for model validation and comparison. Moreover, the statistical size effect influence on fatigue life distribution under constant amplitude loading is explored. Fatigue lives of three materials with different sizes are evaluated respectively, and P–S–N diagrams show that proposed model predictions agree well with the probabilistic scatter bands.

Injection bolts have been used to replace faulty rivets on strengthening operations of old riveted steel bridges. This technology has been essentially tested for its quasi-static or creep b...

A new formulation of a Logistic deterministic S-N curve is applied to fatigue data of metallic materials from ancient Portuguese riveted steel bridges. This formulation is based on a modified logistic relation that uses three parameters to fit the low-cycle- (LCF), finite-life- and high-cycle-fatigue (HCF) regions. This model is compared to the Kohout-Vechet fatigue model, which has a refined adjustment from very low-cycle fatigue (VLCF) to very high-cycle fatigue (VHCF). These models are also compared with other models, such as, power law and fatigue-life curve from the ASTM E739 standard. The modelling performance of the S-N curves was made using the fatigue data considering the stress fatigue damage parameter for the materials from the Eiffel, Luiz I, F�o and Trez�i riveted steel bridges. Using a qualitative methodology of graphical adjustment analysis and another quantitative using the mean square error, it was possible to evaluate the performance of the mean S-N curve formulation. The results showed that the formulation of the S-N curve using the Logistic equation applied to the metallic materials from the old bridges resulted in a superior performance when compared with others models under consideration, both in the estimation of fatigue behaviour in the low-cycle fatigue (LCF) region and in the lowest mean square error.

In this paper, the failure probability of corroded pipelines made by X60 steel grade is evaluated. For this complex real engineering failure problem, the burst corroded performance function is developed using an M5Tree model based on calibration with real burst test database. In addition statistical analysis of ILI-report data is conducted for best modeling of corrosion defects geometries (i.e. defects length and depth) based on Anderson-Darling statistic where different PDFs (i.e. Normal, Lognormal, Frechet, Gumbel, Weibull) were tested. Moreover, the effect of defects geometries on the failure probability of the case-studies were investigated for various operating regimes. Then the influence of distributions on the reliability analysis were also illustrated. Results indicated that increases in defects depth are strongly reduced the safety levels of this problem, where miss-selection of defects distributions could lead to conservatives results.

This study deals with the dynamic response of pipelines under flexural loads. The flexural loads can be harmonic (transmitted by pumps, compressors, etc.) or transient (seismic loads, foundation movement and impact for pipeline inspection). Existing works provide solutions in the frequency domain or in the time domain. However, the methods in the frequency domain cannot simulate the pipeline response under transient loading and the methods in the time domain are mostly based on approximate techniques. An exact solution for pipeline response under transient and harmonic loads is proposed. The modelling of fluid−pipe interaction under transient loading conditions yields coupled equilibrium and motion partial differential equations. Decoupling of the above equations is possible; however, it increases the order of the differential equations from 1 to 4. A system of eight first-order coupled partial differential equations is decoupled, yielding eight fourth-order ones. Integral transforms are used to achieve an analytical solution. The methodology is based on double integral transforms. The implementation of a finite sine Fourier transform for the spatial variable and the analytic inversion of the Laplace transform in the time domain are new. Results are provided for pipelines subjected to impact and harmonic loads.

More than 30 years ago, ENERCON created a unique technology patent in the form of gearless Wind Energy Converter technology. Ever since then, our engineers and specialists have been working continuously to further develop the products and manufacturing processes. We guarantee our customers maximum agility and excellent solutions which make good economic sense and comply with market requirements. Innovations are fundamental to success here. We want to be the first to establish new ideas on the market and new standards in the industry. The expertise of our employees and their interdisciplinary working partnerships form are the essence of our technological excellence. Every day we work to live up to our claim to perform as technology leader. We are leading the way in developing new technologies and taking an active and responsible role in shaping the future of energy generation and supply from renewables. For that we aim to develop and produce the highest-quality wind energy converter on the market. We do not define ourselves primarily in terms of the purchase price, but instead offer turbines with the lowest running costs per unit generated. Content and well-qualified employees are essential for long-term success. That is why we make huge investments in training and advanced training and measures to promote healthy workplaces. The successful further development of our high-tech products relies on us working together. Hybrid towers for ENERCON wind energy converters comprise individual precast concrete elements and steel sections that form the top end of the tower. Concrete segments with large diameters are produced in two or three shells so that they can also be transported to locations which are complex to reach. After all segments and sections have been assembled, the bottom steel section, the concrete segments and the foundation are joined together and tensioned to form one unit by means of prestressing tendons.

An accurate prediction of crack shape development during fatigue propagation plays a key role in structural reliability assessment. To predict crack shape, aspect ratio variability (a/c; a: crack depth, c: half crack length) is wildly used and different correlations to estimate this later exist in literature. In this paper, reliability index of a pipeline with axially surface crack is evaluated. Initial aspect ratio was varied. Tow dimensional crack growth models based on Paris Law coupled to liner elastic fracture mechanics were used. The objective is to clarify the effect of initial aspect ratio and it variability during propagation on the life time prediction of cracked pipeline. Based on Importance sampling, reliability index is plotted against number of load cycle. Results show an important role of initial aspect ratio and crack growth model in reliability index estimation. Calculation of different sensitivity factors illustrates the effect of uncertainty and correlation of Paris law parameters on the predicted life time of the pipeline.

Engineering structures, such as bridges, pressure vessels, machines, etc., are subject to variable load cycles during their lifetime that can cause fatigue damage. Fatigue design of steel structures is based on double S-N curves and the estimation of fatigue damage caused by load cycles. This estimation is calculated by cycle counting methods combined with the Palmgren-Miner rule. The presented software, Fatigue Damage Tool (FDT), is based on the design assumptions of the Eurocode 3 EN1993-1-9 standard. The cycle counting method implemented in FDT is the rainflow counting algorithm according to the ASTM E1049-85 standard, and it uses the Palmgren-Miner rule to calculate de fatigue damage for a critical detail. In this paper, the software is applied to estimate the fatigue damage accumulation for a critical detail at the mid-span of the Varzeas railway bridge. Additionally, FDT can also be applied to several other types of engineering structures.

In the context of fatigue evaluation of riveted railway bridges, cross-girder to main beam connections are frequently critical details. Secondary effects, such as out-of-plane bending and dynamic amplifications due to the proximity to loading paths which in the case of old bridges were not taken into account in the original design, may lead to severe increase of fatigue damage. The fatigue assessment of old riveted railway bridges has been addressed in the last years by developing local models of critical riveted joints that are linked to global models. This local-global modelling approach aims at evaluating local secondary stresses. Former fatigue probabilistic analyses of riveted joints have been focused on resistance variability rather than on loading/stresses (actions) variability. In this paper a probabilistic procedure to include the variability of loading in the fatigue analysis of complex riveted joints of railway bridges is proposed assuming loading as a random variable. Local finite element models were developed and later coupled with the global model in order to obtain the real stresses associated to real trains crossing the bridge. To reduce computational time, the results obtained from these local models were inputted in a Linear Fracture Mechanics model, supported by Paris fatigue crack propagation law. Monte Carlo simulation technique was applied to calculate the fatigue reliability of an old riveted railway bridge, considering traffic records from previous studies on the bridge.

Aero engine components like compressor discs normally operate under harsh conditions like complex multiaxial stress states. Notch effect is often critical for structural integrity assessment in virtue of complex structure and discontinuities. According to the notch effect under cyclic loadings, a computational framework for multiaxial fatigue analysis of compressor discs is established by coupling finite element (FE) simulation of stress gradient with Fatemi-Socie (FS) criterion. Specifically, a notch support extension method accounting for stress gradient effect is elaborated through elasto-plastic FE analysis, which can be determined for fatigue life prediction of arbitrary shaped components. Experimental fatigue data for smooth and notched specimens of TC4 and GH4169 alloys demonstrated the appropriateness of the proposed computational approach. The applicability and performance of the prediction model to a compressor blade-disc attachment subjected to field spectra is presented. Results show that testing effect can be significantly reduced by using this framework with acceptable prediction accuracy.

Aims Several Gastroenterology Societies created recommendations in order to reduce any non-essential exposure to thesevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. The purposes of this paper are 1) to evaluate thenational gastroenterologists' perspective of the impact of COVID-19 and 2) to evaluate the impact of the reorganization ofthe Gastroenterology department of Centro Hospitalar Vila Nova de Gaia/Espinho (CHVNG/E) during COVID-19 Pandemic. Methods For the 1 purpose, an online survey of 32 questions was distributed to gastroenterologists nationwide. For the2 purpose the authors conducted a retrospective analysis of some endoscopic procedures performed at theGastroenterology Department of CHVNG/E between March 16 and May 8 during the years 2019 and 2020. Results 67 gastroenterologists have answered our survey between April 15th and May 5th 2020, mostly females (53.7 %)and 55 to 65 years-old group was the most prevalent (25.4 %). Only 14.9 % were residents. 86.6 % worked in a hospital with COVID-19 patients, with 16.4 % assigned to assist those patients. All the departments had suffered modifications. 90 %of the residents affirmed that their activity has changed mainly endoscopic practice, and 64.2 % respondents agreeing withan internship extension. 94 % declared to have non-essential endoscopic procedures postponed. 85.1 % maintained in-person medical visits, 88.1 % were already having remote consultations and 11.9 % did not have any clinical visit. In ourgastroenterology unit, the number of endoscopic procedures had decreased 73.1 % from 2019 to 2020. Conclusions The advent of the COVID-19 outbreak has led to important changes among Gastroenterology activities inPortugal, and national gastroenterology units are complying with the recommendations. Furthermore, PortugueseGastroenterologists believed that the decrease in endoscopic activity can compromise residents' education and training. Thegastroenterology department at CHVNG/E has shown a significant reduction in the number of endoscopic proceduresperformed during the same period from 2019 to 2020.

Hepatic encephalopathy (HE) is a leading cause of hospita-lization and morbimortality in advanced cirrhosis with limited therapeutic options available. Given the paramount role of gut microbiota in HE, and the efficacy of fecal microbiota transplantation (FMT) in other diseases, this review intends to summarize the evidence supporting the safety, efficacy and future perspectives of FMT in HE. Current evidence, despite being scarce, points towards FMT being a safe, effective and tolerable procedure in HE. Some unanswered questions remain about the optimal dose, the administration route, the long term effects and the selection of the optimal donor. Future trials, some of which are already underway, will provide us additional evidence and hopefully the necessary answers.

Ocean related activities are often supported by offshore equipment with particular power demands. These are usually deployed at remote locations and have limited space, thus small energy harvesting technologies, such as photovoltaic panels or wind turbines, are used to power their instruments. However, the inherent energy sources are intermittent and have lower density and predictability than an alternative source: wave energy. Here, we propose and critically assess triboelectric nanogenerators (TENGs) as a promising technology for integration into wave buoys. Three TENGs based on rolling-spheres were developed and their performance compared in both a “dry” bench testing system under rotating motions, and in a large-scale wave basin under realistic sea-states installed within a scaled navigation buoy. Both experiments show that the electrical outputs of these TENGs increase with decreasing wave periods and increasing wave amplitudes. However, the wave basin tests clearly demonstrated a significant dependency of the electrical outputs on the pitch degree of freedom and the need to take into account the full dynamics of the buoy, and not only that of TENGs, when subjected to the excitations of waves. This work opens new horizons and strategies to apply TENGs in marine applications, considering realistic hydrodynamic behaviors of floating bodies.

Offshore structures are mainly associated with the oil and gas industry given that globally, nearly one-third of the oil and gas extracted worldwide comes from offshore sources. This situation is likely to continue to rise over the coming decades because of abundant deposits of oil and gas still present in the oceans and society's dependency on hydrocarbon fuels. Regardless, offshore wind shows promise and continues to rise at an exponential rate because it provides means for decarbonization while contributing to economic growth in many countries. As such, wind continuos to be a leading solution against climate change globally. To ensure that a structure will fulfill its function, fatigue design is crucial to ensure an adequate service life because it is responsible for more than 80% of structural failures, most of them catastrophic and without warning. This work aims to evaluate environmental loads and fatigue analysis in a jacket-type platform located in the North Sea. Wave data scatter has been provided, and using Morison's formula, the loads on the structure were used to achieve an applicable normal loading force. Then, a static and a dynamic fatigue analysis for the offshore jacket-type structure under consideration are evaluated and compared.

This book chapter intends to provide a fatigue database for some representative materials of old Portuguese metallic bridges (Eiffel, Luiz I, Fao, Pinhao and Trezoi). Puddle irons and structural steels are covered, depending of construction year of the bridge. Besides the base materials, also S–N fatigue data of riveted joints made of original rivets or new rivets are presented, but in any case using original plates. As regards the materials characterization, S–N fatigue data obtained using smooth specimens is presented; also, fatigue crack propagation data obtained using CT specimens is presented. The monotonic tensile properties are also characterized as well as the microstructures. S–N fatigue data for riveted joints was also presented and compared with existing literature data, including existing design curves. This comparison shows some data falling below the design S–N curves that corroborates the presence of cracks originated by the prior operation of the bridge or material degradation. Regarding the strain-life behaviour of the materials investigated, the number of transition reversals decreases with increasing age of the materials. Only the material from the Trezoi bridge shows a transition life typical of low carbon steels. The fatigue crack propagation tests showed that Paris law gives a good description of the fatigue crack growth data with an exponent always greater than 3. The C coefficient was in same range of that recommended in literature for modern construction steels.

The development of numerical simulation for Ultra-high-performance concrete (UHPC) and Ultra-high-performance fiber-reinforced concretes (UHPFRC) is fundamental for the design and construction of related structures. The simplified engineering stress-strain relationship and the input values are necessary in the finite element modeling. Four-linear curves and modified Kent–Park model were proposed to describe the engineering tensile and compressive stress-strain relationship, respectively. An attempt was made to simulate the fracture of UHPC and UHPFRC using concrete damaged plasticity model and element deletion strategies. The predicted tensile and compressive behaviors of UHPC and UHPFRC were successfully validated by the test results in the literature. For a better understanding of the mechanical behavior of UHPC and UHPFRC exposed to biaxial loadings, mixed-mode crack propagation simulation on the double-notched specimens exposed to combined shear-tensile and shear-compressive forces was discussed.

The fatigue resistance of welded connections made of high strength steel (HSS) is one of the most important topics for the application of HSS in the construction sector. One of the most challenging issues is how to predict the fatigue life of welded structures with complex geometry based on the test results from relatively simple coupon specimens. However, there are generally pre-existing residual stresses in the welded coupon specimens during fatigue tests, and these residual stresses vary greatly in welded structures with complex geometry. This increases the difficulty in predicting the fatigue behaviour of welded structures based on results at coupon scale. Hence, it is important to establish a relationship between the residual stress independent material characteristics and fatigue life. The fatigue behaviour of complex welded structures can be predicted by this residual stress independent material characteristics calibrated at the coupon level and simulated local residual stress distribution. In this paper, the residual stress-free characteristics, hardness, is employed to predict the fatigue life of butt-welded joints. Besides, the residual stress of V-shaped butt welds on a plate made of high strength steels are analysed by modelling of the welding process based on subsequent thermal analysis and mechanical stress analysis by implementing kill/birth strategies. The results show that it contributes to a better prediction compared with experimental results after considering the residual stress effects.

Wire arc additive manufacturing (WAAM) has increasingly attracted attention in the construction sector because of its ability to produce large metallic structural parts in short times. In this paper, Coffin-Manson and Morrow (CMM) equation is employed to compare the fatigue life of WAAM stainless steel with the structural steels S355 and S690. The results showed that the fatigue performance of structural steel is better than the WAAM stainless steel, the fatigue performance vertical to printing direction (WAAM-900) is better than it along the printing direction (WAAM-00). In addition, the fatigue cycle of the transition reversals of structural steel is much less than it of WAAM stainless. With the increasing the fatigue cycle, the maximum density of the strain amplitude ratio is gradually increased to 1.0. The probabilistic parameters of CMM equation were obtained by a stochastic analysis using Latin hypercube sampling strategies. The probabilistic strain-fatigue life behaviour obtained from the constant exponent sampling strategy is higher when compared with the varied exponent sampling strategy for both WAAM stainless and structural steels.

The ductile performance of high strength steel (HSS) from different steel grades, producers, manufacturing processes varies a lot. It is also difficult to conduct all kinds of reliable experiments to generate different stress status through different initial specimen geometries or by applying different load combinations in the civil engineering sector. One of the common issues for HSS structures is to identify the parameters of the ductile fracture model conveniently from the uniaxial stress–strain relationship obtained from common coupon specimens. An attempt is made in this paper to use the proposed mesoscale critical equivalent plastic strain (MCEPS) to calibrate the fracture locus of the uncoupled phenomenological model based only on the engineering stress–strain relationship. The proposed method is successfully validated by the Sandia fracture challenge in 2014.

The wind resource offshore is often excellent due to a higher average wind speed and lower turbulence intensity. Jacket structures are the most common offshore platforms for extraction of oil and natural gas in relative low water depths. When the offshore resources run out, these structures must be displaced to another area containing underground resources or removed in the case of reaching their design life. Therefore, one possible procedure to reduce the carbon footprint on the planet, allowing society to rely on promising sources of ’clean’ energy while salvaging these oil and gas platforms, is to consider the transformation of these oil and gas platforms into offshore wind turbine support structures. The present research focus on the possibility of converting such structures for gas extraction into offshore platforms for wind turbines. In this study, a comparison between the behavior of horizontal and vertical axis wind turbines on the same offshore platform is presented. In this comparison, two different software programs are used: MATLAB and SAP2000. The model proposed is a new simplified tool used to study the structural analysis of the jacket structures, developed and summarized in 10 steps, adopted to evaluate the behavior of the platform with the wind tower configurations.

This paper introduces the assessment method for ergonomic interaction design reliability of the engineering software operation flow in the field of civil engineering. On basic structure of ...

In North America and Europe, there is a significant number of centenary metallic bridges that require maintenance and strengthening operations. These structures need to be adapted to increasing traffic intensities, and their structural integrity should be constantly evaluated. Fatigue damages were not considered in the original design of old metallic bridges, and riveted connections are one of the most frequent sources of fatigue damages on these structures. This paper intends to be a contribution for the reliable assessment of the fatigue behavior of riveted connections by proposing S-N curves for these structural details. Experimental fatigue data is analyzed from multiple bridges across Europe, and different statistical methods were implemented. A normal distribution function was implemented following the ISO 12107 standard, and the results were compared with the implementation of the two-parameter Weibull distribution function. Different estimation methodologies were implemented to determine the parameters of the Weibull distribution. S-N curves obtained by the statistical analysis were then compared with design recommendations from North American and European standards.

The paper deals with the subject of diagnostics and the quick repairs of long-term operated metallic materials. Special attention was paid to historical materials, where the structure (e.g., puddle iron) is different from modern structural steels. In such materials, the processes of microstructural degradation occur as a result of several decades of exposure, which could overpass 100 years. In some cases, their intensity can be potentially catastrophic. For this reason, the search for minimally invasive diagnostic methods is ongoing. In this paper, corrosion and fracture toughness tests were conducted, and the results of these studies were presented for two material states: post-operated and normalized (as a state &ldquo, restoring&rdquo, virgin state). Moreover, through the use of modern numerical methods, composite crack-resistant patches have been designed to reduce the stress intensity factors under cyclic loads. As a result, fatigue lifetime was extended (propagation phase) by more than 300%.

This paper addresses the dynamic behavior of the La Scarpe viaduct, which consists of a continuous nine-span steel–concrete composite bridge belonging to the French HSR line TGV Nord. The ...

Racking systems applied in logistics warehouses are built with thin steel sections that are joined by bolted connections. In fully automatic systems, these structures are loaded 7/7 days and 24/24 hours raising fatigue issues due to the cyclic nature of the resulting stresses. According to the current industrial practice, those bolted joints are tight with no torque control, leading to the concept of snug tight bolts, which behaves similarly to non-preloaded bolted joints. Eurocode 3 has no reference about fatigue rules of bolted connections between thin-walled cold formed steels. This paper aims at analyzing the fatigue behaviour of bolted (snug tight vs. preloaded) joints in order to provide fatigue design rules for possible update of Eurocode 3 existing rules. A significant fatigue testing program was performed to investigate the influence of different bolts arrangements, stress R-Ratios and bolt preloads, including snug tight, on fatigue life. The obtained results were analyzed under ASTM E739 procedure in order to obtain S-N curves. This work revealed an average fatigue strength of 114 MPa at 2E6 cycles for the snug tight bolted joints. Preloaded bolt joints presented an average fatigue strength of 108 MPa at 2E6 cycles. Discrepancies between S-N curves suggested by Eurocode 3 and fatigue data obtained experimentally were verified.&nbsp

Preserving the structural integrity of historical bridges made of wrought iron is a mandatory technical requirement in several countries in Europe. A reliable fatigue lifetime estimation of...

Design optimization of fiber-reinforced polymeric (FRP) composite products is essential to facilitate their applications in engineering structures. For bridge structures, the main design optimization goals are the reduction of FRP material consumption and the structure weight, which aim to reduce the initial construction cost and achieve a longer bridge span. Compared with conventional steel–concrete composite bridges, FRP-steel composite bridges possess more design variables and more complex design process, which necessitate the simplified optimization models. This paper aims to propose a two-scale design optimation method for FRP bridge deck on the steel girder. The macro behavior of the pultruded FRP composite bridge deck is analyzed. Regarding the micro level, the equivalent properties of pultruded GFRP lamination are calculated by combining micromechanics and classical lamination theory (CLT). The above-mentioned macro pultruded GFRP bridge level and the micro fiber/resin level were bridged based on the assumption that the micro-component effective homogenized strain equals to the corresponding macro strain. The two-scale lamination optimization of pultruded GFRP bridge deck is finally achieved by finding optimized two-scale design variables that can achieve the minimum bridge weight or the lowest initial construction cost with all listed constraint requirements satisfied. A pultruded FRP deck supported on equally-spaced steel girders was selected as a case study to show how to obtain the optimized two-scale parameters by using this proposed optimization method. The optimized results of the top flange thickness, tu, the bottom flange thickness, tl, the web height, hw, and the web thickness per meter, tw, are 46.02 mm, 45.86 mm, 300.0 mm and 37.42 mm, respectively. Results also showed that the optimized ratio of the 0°-lamina, 45°-lamina, and the 90°-lamina are77.9%, 17.1%, 5.0%. The optimized fiber volume fraction is 65.2%.

Owing to the superior mechanical performance and material efficiency, the combination of prestressed concrete (PC) slabs and corrugated steel webs (CSW) as PC girder with CSWs (PCGCSW) is extensively applied to railway and highway bridges. To overcome the shortcomings of traditional balanced cantilever construction (TBCC) of PCGCSW, reduce environmental impact, and promote sustainable construction, a novel asynchronous-pouring-construction (APC) technology is introduced in this paper. This improved method makes full use of the excellent shear capacity of the corrugated steel webs (CSWs) to support the hanging basket, increases the construction platforms to accelerate the construction speed. Based on a practical project of a long-span composite box girder bridge with CSWs in China, the construction process of the APC method is systematically introduced, and the structural safety and environmental sustainability of such bridge using APC technology are evaluated and compared with that using TBCC. The comparison results indicate that APC method can reduce the compressive stress of top concrete slab, but slightly increase the shear stress and deflection during the cantilever construction stage because the hanging basket is directly supported by CSWs. Besides, the weight of the improved handing basket in APC technology is reduced up to half in comparison that in TBCC. Accordingly, the APC technology saves a lot of energy consumption, reduces huge CO2 emissions for construction equipment, and shorts construction period. Therefore, the utilization of APRC technology can ensure the bridge's safety and reliability, effectively accelerate construction speed, reduce the construction load, decrease the environmental pollution, and save the engineering cost, which can be regarded as a sustainable and environmental-friendly construction method for composite bridges with CSWs.

This thematic issue on advanced simulation tools applied to materials development and design predictions gathers selected extended papers related to power generation systems, presented at the XIX International Colloquium on Mechanical Fatigue of Metals (ICMFM XIX) organized at University of Porto, Portugal, in 2018. Guest editors express special thanks to all contributors for the success of this special issue—authors, reviewers, and journal staff.

The fatigue crack growth (FCG) has been widely studied by the scientific community. There are several proposed FCG models, the best known being the Paris relation. The fatigue crack initiation and propagation have been studied separately, however, researchers have made an effort to study the relationship between these two fatigue phenomena. In this sense, several fatigue crack growth models based on local approaches have been proposed, the UniGrow model being well-known. The fatigue crack growth process is assumed a succession of crack re-initiations considering a certain elementary material size. Recently, Huffman developed a strain energy density based on Walker-like stress life and fatigue crack growth behavior. In this paper, the Huffman model based on local strain energy density is used to predict the fatigue crack initiation and propagation for the P355NL1 pressure vessel steel. This model is combined with the generalized probabilistic fatigue model proposed by Correia aiming the generation of probabilistic fatigue crack initiation and propagation fields. In this study, the local stress and strains at the crack tip were obtained combining linear-elastic and elastoplastic analyses. The probabilistic fatigue crack growth rates fields for several stress R-ratios are estimated considering strain, SWT, and equivalent stress amplitude damage parameters. A comparison between the experimental FCG data and the generated probabilistic FCG fields is made with very satisfactory correlations being found.